PSAS 2012
International Conference on Precision Physics
of Simple Atomic Systems 2012
Eltville, Germany -
Information

Title:	Dr.
Family Name:	Antognini
First Name:	Aldo
Gender:	male
E-Mail:	aldophys.ethz.ch
Affiliation for Badge:	ETH Zurich
Institute:	ETH Zurich
Address (Street):	Schafmattstr. 20
Postal Code, City:	8093 Zurich
Country:	Switzerland
Phone:	+41 44 633 30 76
Fax:
Arrival Date:	June 10
Departure Date:	June 15
Excursion with Conference Dinner:	Selected
Payment:	Bank transfer to GSI
Title:	Charge, Zemach and magnetic radius of the proton
Abstract:	The comparison between theory and experimental values for the 1S Lamb shift and HFS in hydrogen is currently hampered by the lack of accurate knowledge of the proton structure: the rms charge radius $r_E$ and the Zemach radius $r_Z$, respectively. Spectroscopy of muonic hydrogen provides precise determinations of these parameters. Two transition frequencies have been measured in muonic hydrogen between the 2S and the 2P states: $\nu_s$ starting from the singlet and $\nu_t$ from the triplet 2S-state. The combination $3/4\,\nu_t+1/4\,\nu_s$ leads to a determination of the "pure" 2S-2P Lamb shift (without 2S-HFS effects) with a relative accuracy of $u_r=1\times 10^{-5}$, whereas the difference $\nu_t-\nu_s$ leads to a determination of the 2S-HFS with $u_r=2\times 10^{-4}$. From the "pure" Lamb shift, when experimental value and theoretical prediction are compared, an improved value of $r_E$ is obtained with $u_r=7\times 10^{-4}$ limited by theory. Our previous result [Pohl et al., Nature 466 (2012) 213], which is at variance by 7 standard deviations from the CODATA value, is confirmed. The discussion around this discrepancy will be presented. Likewise, via the HFS, we will determine $r_Z$ with $u_r=3\%$ and from it, under a model assumption of charge and magnetic distributions, the magnetic radius $r_M$ of the proton is extracted. The obtained $r_Z$ is consistent with the determinations from hydrogen spectroscopy and scattering experiments. This implies that the measured HFS in muonic hydrogen agrees with its theoretical prediction.

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